This late 1860s carte de visite (CDV) of a girl holding a doll is an early example of an enameled photograph.

Enameled photographs first appeared (in the US) in the 1860s as a way to protect albumen photographs. The process left the photograph with a thin transparent layer to protect the photographic image. The photograph was glossy in appearance, could be wiped with a moist cloth and wouldn't show moisture damage.

The first US patent that I could find for the process is in 1867 by Nathaniel Weston of San Francisco, CA:

My posted CDV was probably made using the Weston process as J.T. Silva and Weston were contemporaries in the SF area.

The enamel process has done an excellent job in preserving the photograph. The typical age spots or foxing is not found in this particular image. However, the process does leave CDVs with a slight warped or curved appearance-- the tell tale sign of an enameled card.